Human Growth Hormone, hGH, is a protein consisting of a single chain of 191 amino acids. The molecule is cross-linked by two disulfide bridges and the monomeric form has a molecular weight 22 kDa. hGH preparations have been prepared from human pituitaries, but nowadays the products on the market are produced by recombinant methods, rhGH. Two types of therapeutically useful recombinant hGH preparations are present on the market: the recombinant hGH, e.g. Genotropin®, Pharmacia AB, and an analogue of the recombinant hGH with an additional methionine residue at the N-terminal end, e.g. Somatonorm®. hGH is used to stimulate linear growth in patients with hypopituitary dwarfism or Turner's syndrome but other indications have also been suggested.
Growth hormone therapy is used in children to promote growth and in adults to improve muscle strength, reduce fat mass and improve metabolic profiles, which could predispose to cardiovascular disease. In contrast to the growth promoting effects of growth hormone, the metabolic effects have been less often studied, yet they may be very important to the risk-benefit assessment of GH therapy in adults.
GH therapy is known to counter insulin actions and is contra-indicated for individuals with diabetes mellitus.
At present GH therapy in adults is monitored using serum IGF-I levels, but it is possible that it is the metabolic effects which are more relevant to improvements in symptomatology and disease risk profiles and there is a need to develop ways of formally assessing these responses.